CURING KINETICS AND PROPERTIES OF ACRYLIC RESIN CURED WITH AZIRIDINE CROSSLINKER

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Crystal Growing Techniques

Techniques"Crystal growing is an art." Not.The techniques chosen depends less on "art" and "intuition" than on the chemical properties of the compound of interest:∙Is the compound hygroscopic?∙What are the compound's solubility properties?∙Is the compound air or light sensitive?∙What about decomposition?∙etc. etc. etc.∙Slow EvaporationSimplest way ro grow compounds and works well for compounds that are not sensitive to ambient conditions in the laboratory.- Prepare a solution of the compound in a suitable solvent (saturated or nearly saturated)- Filter the solution through a clean glass frit into a clean vessel* and cover, but not tightly.- Gently put the container in a quiet, out of the way place and allow the solvent to evaporate slowly.- This method works best when there is ample material to allow for at least a few milliters of solvent.∙Slow CoolingThis method works well for solute-solvent systems which are less than moderately soluble and the solvent's boiling point is less than 100o C.- Working with a saturated solution: No Dust/Hair etc., Heat thesolvent to boiling point or slightly below it. Transfer by filteringthrough a warm frit into a vessel* (test tube, or scintillation vial) and stopper tightly. Transfer vessel to flask in whcih hot water* (oil may also be used) has been heated to a couple of degrees below the solvent boiling point.- The water level should exceed the solvent level in the vessel butshould not exceed the height of the vessel (or you can use athermostated oven).∙Variations on Slow Evaporation and Slow Cooling If these techniques do not yield suitable crystals from single solvent systems, these techniques can be expanded to binary, tertiary, and even quaternary solvent systems.- The basic rationale is that by varying the solvent composition, growth of certain crystal faces may be inhibited while the growth in some other direction is promoted, thus yielding crystals of suitable morphology and size.- Reproducibility is paramount in science! Growing crystals frommultiple solvent systems will be imprecise unless solvent compositions are recorded.... hence "art."∙Liquid Diffusionvery sucessful method for obtaining single crystals of organiccompounds*- A small amount of solution is placed in a tube, and a suitableprecipitant is layered carefully down the side of the tube onto thesolution. It is very important that this second liquid be less dense than (or visa versa*), and miscible with, the solvent.- The volume ratio solvent:ppt will be variable, but a good place to start is 1:4 or 1:5.- Slightly turbidity should form at the interface- If there is no crystal growth after 24 hr, try a more concentratedsolution∙Use of Seed CrystalsThis method is useful when other methods provide crystals which,although of reasonable quality, are too small. These small crystals can be used as "seed" crystals in a slow cooling saturated solution.- Draw the seed crystals in a pipette together with some mother liquor (do not allow the seed crystals to dry!)- Carefully deposit these "seed crystals" in the saturated solution.The fewer the "seeds" the bigger the resulting crystals∙ConvectionThis is a less standard method, but one may attempt to grow crystals by convection by creating a thermal gradient in the crystal growing vessel.The theory behind this method is that the solution becomes moresaturated in the warm part of the vessel and is transferred to the cooler region where nucleation takes place. To create convection, one must use either local heating ot local cooling.- Trick to making this easy:MeCN/Et2O hot frit∙CounterionsIf your compound is ionic and is not giving suitable crystals with agiven counterion, perform a metathesis reaction to change thecounterion.- Ions of similar size tend to pack better and subsequently give better crystals∙Ionization of Neutral CompoundsIf the compound of interest is neutral and contains proton donor or acceptor groups, better crystals may be grown by first protonating or deprotonating the compound.- The ionic form of the compound could take advantage of factors such as hydrogen bonding to yield better crystals. Of course, this will alter the electronic properties of your compound, but if a generalconformation is what is needed from the structrue determination, then this should not be a problem.ReferencesCrystals and Crystal Growing, Alan Holden and Phylis Singer, Anchor Books-Doubleday, New York, 1960.The Growth of Single Crystals, R. A. Laudise, Solid State Physical Electronic Series, Nick Holonyak, Jr. Editor, Prentice-Hall, Inc., 1970.。

专业英语

questions
How
do you distinguish steel from cast iron? How do you distinguish low alloy steel from high alloy steel?
1.1.1 Iron and Steel
The earth contains a large number of metals which are useful to man. One of the most important of these is iron. Modern industry needs considerable quantities of this metal, either in the form of iron or in the form of steel.
Mechanical Engineering materials
Organic polymer materials Inorganic non-metallic materials
plastic rubber Synthetic Fibers Traditional ceramics Special Ceramics Metal Matrix Composites
1.1.1 Iron and Steel
The ore becomes molten, and its oxides combine with carbon from the coke. The non-metallic constituents of the ore combine with the limestone to form a liquid slag. This floats on top of the molten iron, and passed out of the furnace through a tap. The metal which remains is pig iron.

14行诗英语

14行诗英语The 14-Line PoemPoetry has long been a cherished form of artistic expression, captivating the hearts and minds of readers and writers alike. The 14-line poem, often referred to as a sonnet, holds a special place in the literary landscape, boasting a rich history and a unique structure that has inspired countless poets throughout the ages.At its core, the 14-line poem is a concise and powerful medium that allows the poet to explore a single theme or idea in depth. The traditional structure, which originated in Italy during the 13th century, typically follows a specific rhyme scheme and meter, creating a harmonious and rhythmic flow that carries the reader through the poem's narrative.One of the most striking features of the 14-line poem is its ability to convey complex emotions and ideas within a compact form. The poet must carefully select each word and phrase, crafting a tapestry of language that is both visually and intellectually engaging. The structure, with its three quatrains and a final couplet, provides a framework for the poet to develop a central theme or argument,building towards a climactic resolution or insight.The enduring popularity of the 14-line poem can be attributed to its versatility and adaptability. While the traditional Petrarchan and Shakespearean sonnets have become iconic, poets have also experimented with variations on the form, such as the Spenserian and the Curtal sonnet, each with its own unique twist on the classic structure.In the hands of a skilled poet, the 14-line poem can be a powerful tool for exploring the human experience in all its complexity. From the depths of love and loss to the contemplation of philosophical questions, the sonnet has the ability to capture the essence of the human condition in a concise and captivating manner.One such example is William Shakespeare's famous "Shall I compare thee to a summer's day?", a timeless ode to the enduring power of love. In just 14 lines, Shakespeare weaves a tapestry of imagery and emotion, comparing the beauty of his beloved to the fleeting nature of summer, and ultimately proclaiming the immortality of love through the enduring medium of poetry.Similarly, John Keats' "On First Looking into Chapman's Homer" is a masterful exploration of the transformative power of literature. Through vivid descriptions and a sense of awe, Keats transports thereader to the moment of discovery, when the beauty and wonder of Homer's epic poetry is revealed to him for the first time.The 14-line poem has also been a favored form for poets exploring more abstract or philosophical themes. In "Ozymandias," Percy Bysshe Shelley presents a powerful meditation on the transience of human power and the inevitable decay of empires. By juxtaposing the towering grandeur of a once-great ruler with the desolate reality of his fallen kingdom, Shelley crafts a poignant commentary on the fleeting nature of human ambition and the enduring power of art.Beyond the traditional themes of love, nature, and philosophy, the 14-line poem has also been used to address social and political issues. In "Nuns Fret Not at Their Convent's Narrow Room," William Wordsworth offers a reflection on the power of constraint and limitation, suggesting that it is within the confines of form that true creativity and insight can flourish.In the contemporary era, the 14-line poem continues to captivate and inspire new generations of poets. From the haunting lyricism of Sylvia Plath's "Daddy" to the intricate wordplay of Seamus Heaney's "Digging," the sonnet form remains a vital and enduring part of the literary landscape.As we delve into the rich tapestry of the 14-line poem, we arereminded of the timeless power of language to express the full range of human experience. Whether exploring the depths of emotion or the complexities of the human condition, the sonnet remains a testament to the enduring artistry of poetry and the enduring fascination of the written word.。

Investigation of crystal growth kinetics

Investigation of crystal growthkineticsIntroductionCrystal growth is a process that involves the formation of crystal structures from a homogeneous solution or melt. The study of crystal growth kinetics is important in terms of understanding the fundamental principles underlying the processes of nucleation and crystal growth, as well as in the development and optimization of crystal growth techniques and the design of new materials.NucleationNucleation is the initial stage in crystal growth that involves the formation of small clusters or nuclei of the crystal phase in the supersaturated solution or melt. The rate of nucleation is dependent on several factors including temperature, concentration, degree of supersaturation, and the presence of seed crystals.The classical theory of nucleation postulates that the free energy required for the formation of a nucleus is proportional to the volume of the nucleus raised to the power of 2/3. This implies that the formation of larger nuclei requires much higher free energy, which in turn leads to a decrease in the rate of nucleation. Changing the crystallization conditions can affect the kinetics of nucleation, and a detailed understanding of this process is essential for controlling the formation of crystals with specific properties.Crystal GrowthOnce nuclei are formed, crystal growth proceeds through the addition of atoms or molecules to the growing crystal surface. The rate of crystal growth is dependent on the concentration of solute in the solution, temperature, and other factors such as agitation or the presence of impurities.Crystal growth can either be diffusion-controlled or surface-controlled. In diffusion-controlled growth, the rate of crystal growth is limited by the rate of diffusion of solute to the growing surface. Surface-controlled growth, on the other hand, is limited by the rate of attachment or detachment of solute molecules at the crystal surface.Crystal Growth KineticsThe kinetics of crystal growth can be described by several models, including the Avrami equation, the Ostwald–de Waele model, and the Lifshitz–Slyozov–Wagner model. These models are based on assumptions about the mechanisms of crystal growth and have different mathematical forms.The Avrami equation is one of the most widely used models for describing the kinetics of crystal growth. It is based on the assumption that the growth of crystals is a random process, and the rate of growth of a crystal is proportional to the number of crystals present in the solution or melt.The Ostwald–de Waele model assumes that crystal growth is a power-law process, and the relationship between the growth rate and the concentration of solute in the solution follows a power law. This model is particularly useful for describing the kinetics of crystal growth in systems where diffusion is the rate-limiting step.The Lifshitz–Slyozov–Wagner model is based on the assumption that crystal growth occurs through the coalescence of smaller crystals into larger ones. This model is useful for understanding the mechanisms underlying the formation of large single crystals from a solution or melt.ConclusionIn conclusion, the study of crystal growth kinetics is an important area of research that is essential for the development of new materials and the optimization of crystal growth techniques. The kinetics of nucleation and crystal growth are dependent on several factors such as temperature, concentration, and the presence of impurities, and can be described by several mathematical models. A detailed understanding of thekinetics of crystal growth is essential for controlling the formation of crystals with specific properties and for the design of new materials with novel properties.。

Investigating the Kinetics of Crystal Growth

Investigating the Kinetics of CrystalGrowthCrystals are fascinating objects, both in terms of their beauty and their properties. They are used in a wide variety of fields, including electronics, mechanics, and medicine. However, their growth is a complex process that is not fully understood. Investigating the kinetics of crystal growth is therefore a crucial step in developing new materials and improving existing ones. In this article, we will explore the different factors that influence crystal growth kinetics and how they can be measured.Introduction to Crystal GrowthBefore diving into the kinetics of crystal growth, it is important to understand what the process entails. Crystal growth is the formation of a solid material with a well-defined structure from a liquid or gaseous phase. This process can occur naturally, such as in the formation of snowflakes or gemstones, or it can be artificially induced, as in the production of silicon wafers or pharmaceuticals.Crystals are formed by the repeated pattern of atoms or molecules, called the unit cell, that make up the crystal lattice. The rate at which this lattice grows determines the size and shape of the crystal. A crystal can exhibit different morphologies, such as cubic, hexagonal, or tetragonal, depending on the conditions of its growth.Factors Affecting Crystal Growth KineticsThe kinetics of crystal growth are influenced by a multitude of factors, including temperature, concentration, and substrate properties.Temperature: The rate of crystal growth increases with temperature, as the thermal energy of the system provides more movement to the atoms or molecules and allows them to arrange themselves into the crystal lattice more quickly. However, the temperature must not be too high, as this can cause defects or even melt the crystal.Concentration: The concentration of the solution or gas from which the crystal is growing also affects its kinetics. In general, higher concentration leads to faster crystal growth, as there are more building blocks available to form the lattice. However, there is a limit to this effect, as overcrowding can lead to irregular growth and the formation of multiple crystals.Substrate Properties: The substrate on which the crystal grows can also influence its kinetics. The surface chemistry and topography of the substrate can affect the nucleation of the crystal and the direction of its growth. A rough substrate can lead to an irregular or faceted crystal morphology, while a smooth substrate can result in a more uniform structure.Measuring Crystal Growth KineticsTo investigate the kinetics of crystal growth, several methods can be used to monitor the changes in the crystal morphology and size over time.Optical Microscopy: Optical microscopy is a commonly used technique to visualize the growth of crystals in situ. The microscope can be equipped with polarizing filters to enhance the contrast between the crystal and its surroundings. By capturing images of the crystal at regular intervals, the growth rate and morphology can be measured.X-Ray Diffraction: X-ray diffraction is a technique that can provide information on the crystal structure and its changes over time. It works by shining a beam of X-rays on the crystal and measuring the diffraction pattern that results from the interaction of the X-rays with the atoms in the crystal. By analyzing the diffraction pattern, the crystal lattice parameters and the presence of defects can be determined.Atomic Force Microscopy: Atomic force microscopy (AFM) is a high-resolution imaging technique that can be used to measure the surface topography of a crystal. By scanning a sharp tip over the crystal surface, AFM can provide information on the height and shape of the crystal at the nanometer scale. This technique can also reveal the presence of defects or impurities on the crystal surface.ConclusionIn conclusion, investigating the kinetics of crystal growth is a crucial step in understanding the properties and behavior of crystals. The rate and morphology of crystal growth are influenced by various factors, including temperature, concentration, and substrate properties. Measuring these kinetics requires the use of different techniques, such as optical microscopy, X-ray diffraction, and atomic force microscopy. By improving our understanding of crystal growth, we can develop new materials with tailored properties and improve existing ones for a wide range of applications.。

The Melody of Melancholy

Title: The Melody of MelancholyIn the vast expanse of human experience, the melody of melancholy is a poignant symphony that echoes through the corridors of time, evoking a deep sense of introspection and reflection. As the philosopher Friedrich Nietzsche famously declared, "The only thing that you absolutely have to know is the location of the library." This essay delves into the essence of melancholy, its role in human growth, and the significance it holds in shaping our collective destiny.The term "melody" refers to a sequence of musical notes that forms a piece of music, often used to describe a harmonious and pleasing sound. In the context of melancholy, the melody represents the harmonious yet melancholic notes that resonate within us, evoking a deep sense of introspection and reflection. It is the poignant symphony that echoes through our hearts, reminding us of the profound connection and bond that melancholy creates.The melody of melancholy is a universal and timeless sentiment that binds humanity together. It is the harmonious yet melancholic notes that resonate within us, fostering a sense of unity and understanding. It is the poignant symphony that echoes through our hearts, reminding us of the profound connection and bond that melancholy creates. As the poet John Keats famously wrote, "A thing of beauty is a joy forever: its loveliness increases; it will never pass into nothingness." The melody of melancholy is the reminder of our shared humanity, the beauty that endures and inspires us to strive for a more compassionate world.Throughout history, the melody of melancholy has been a recurring theme in literature and philosophy. It is the exploration of the human condition, the acknowledgment of our shared experiences of pain and loss. The story of the mythical Phoenix, for instance, illustrates the concept of the melody of melancholy, where death and rebirth are seen as part of a continuous cycle of life.In the modern world, the melody of melancholy continues to play a significant role in shaping our lives and interactions. It is the harmonious yet melancholic notes that guide us in our daily interactions, reminding us to treat others with kindness and understanding. The melody of melancholy is the reminder of our shared humanity, the beauty that endures and inspires us to strive for a more compassionate world. In conclusion, the melody of melancholy is a timeless and universal concept, one that transcends time and space. It is the harmonious yet melancholic notes that resonate within us, evoking a deep sense of introspection and reflection. As we navigate the complexities of the modern world, let us remember the melody of melancholy, for it is the reminder that we have the power to shape our own destiny, to transform adversity into strength, and to create a more compassionate world. In the melody of melancholy, we find not just a source of inspiration but a beacon of hope that inspires us to dream, to strive, and to believe in a brighter future.。

我心目中的科学家英语作文范文

我心目中的科学家英语作文范文In my view, scientists are akin to modern-day alchemists, weaving intricate narratives of discovery within the fabric of the universe. They are the navigators of the unknown, wielding curiosity as their compass and reason as their sail. Let me take you on a journey through the corridors of my mind, where the portrait of a scientist unfolds in vibrant hues of intellect and ingenuity.Imagine a world where equations dance across chalkboards like cosmic ballets, where the language of atoms whispers secrets only the keenest ears can decipher. This is the realm of the scientist, where every question is a breadcrumb leading to the banquet of knowledge. They are the architects of understanding, building bridges between the tangible and the intangible.At the heart of scientific inquiry lies a relentlesspursuit of truth. It is a quest fueled not by ego, but by an insatiable hunger to unravel the mysteries of existence. From the microscopic dance of particles to the grandorchestration of galaxies, scientists peer through the veil of ignorance, seeking to illuminate the darkness with the torch of reason.Yet, amidst the chaos of experimentation and the labyrinth of data, there exists a quiet humility. For every answer uncovered reveals a dozen new questions, each more tantalizing than the last. The scientist is a humble pilgrim, journeying ever deeper into the unknown, guided by the twin beacons of curiosity and skepticism.But make no mistake, theirs is not a solitary endeavor. Science is a tapestry woven from the threads of collaboration and cooperation. Across continents and disciplines, scientists join hands in a symphony of discovery, harmonizing their efforts to conquer the frontiers of knowledge. In this global chorus, no voice is too small, no contribution too insignificant. For it is in diversity that the true power of science resides, drawing strength from the myriad perspectives that illuminate the path forward.And yet, for all their brilliance, scientists are not immune to the foibles of humanity. Egos clash like tectonic plates, and dogma can obscure the light of reason. But in the crucible of debate and discourse, truth emerges triumphant, tempered by the fire of scrutiny.So, what then defines the essence of a scientist? Is it the accolades adorning their walls or the equations etched in their minds? Perhaps it is neither, but rather the spark of curiosity that ignites their soul. For in the end, it isnot the destination that defines us, but the journey we undertake in pursuit of understanding.In my eyes, the scientist is more than a mere mortal; they are the custodians of curiosity, the stewards of skepticism, and the architects of enlightenment. They are the poets of the cosmos, crafting verses of truth in the language of the universe. And as long as there are questions left unanswered, their quest shall endure, a testament to the indomitable spirit of human intellect.。

对乔姆斯基语言学科学性的质疑——回应王强和Chomsky的批评

2006年第4期外国语总第164期No．4．J u l y 2006 J ou r n al of F o r e i g n L a n g u a g e s GenerM Serial No．164文章编号：1004—5139(2006)04—0047—10中图分类号：H0—06 文献标识码：A 对乔坶斯基语言学科掌性的质疑——回应王强和Chomsky的批评睾石毓智(湖南师范大学外语学院，长沙410081；新加坡国立大学)摘要：王强的文章对我们前文《乔姆斯基语言学的哲学基础及其缺陷：}进行了全面的批评，而且他还把我们前文的内容转述给了乔姆斯基本人，在王文中共引用了12段乔氏针对我们前文的批评意见。

王文为乔姆斯基语言学的科学性进行了全面辩护。

本文从一般的科学研究方法和语言现象的本质特征等角度，对转换生成语言学的科学性提出进一步的质疑，同时又阐释我们的语言能力合成说的根据和意义。

关键词：乔姆斯基；哲学基础；公理化方法；认知语言学；语言能力合成说The Deficiency of Chomskyan Linguistics_____·_·___-___—_A Discuss ion with W A NG Qiang and ChomskysHI Yu．zhi(Hunam Normal University；National University of Sing apore)Ab s tr a ct：T h e article by WANG Qiang，w hic h contains 12 paragraphs of Chom sk y’8c o m m e n t s particularlyp re v i o u s pape r has comp re he nsi ve ly c r it ic i ze d analyses o n generative linguistics．They claim that Chomsk)7all li n·guistics is s ci en ti fi c，s at is fy in g the features of all sciences．This paper argues against them the basis of the me th od- ology of sc i en c e s and o u r unders ta ndi ng the n a t u re of language．In addition，the hypothesis of”compositionality of ling ui st i c compe te nce”is defended，empi rica lly and theoretically．K ey w o rd s：C h o m sk y；p h i l os o p h ic a l f oun dat ion；a xiom ati c meth odo log y；cog nit ive linguistics；compositionality of linguistic compete nce一、引育直接对话。

我对纳米技术用在琥珀上的看法作文

我对纳米技术用在琥珀上的看法作文英文回答：Nanotechnology is a rapidly advancing field that has the potential to revolutionize various industries,including the jewelry industry. When it comes to amber, a fossilized tree resin known for its beauty and historical significance, nanotechnology can offer numerous benefits.First and foremost, nanotechnology can be used to enhance the appearance of amber. By manipulating the size and arrangement of nanoparticles on the surface of amber, scientists can create unique visual effects, such as iridescence or color-changing properties. This can make amber jewelry even more visually appealing and desirable.Additionally, nanotechnology can be employed to improve the durability and strength of amber. By incorporating nanoparticles into the resin matrix of amber, it can become more resistant to scratching and cracking. This wouldensure that amber jewelry remains in pristine condition for a longer period of time, increasing its longevity and value.Furthermore, nanotechnology can enable the developmentof self-cleaning amber. By coating the surface of amberwith a thin layer of nanoparticles that possess self-cleaning properties, dust, dirt, and other contaminants can be repelled. This would greatly reduce the need forfrequent cleaning and maintenance of amber jewelry, makingit more convenient for the wearer.Moreover, nanotechnology can facilitate the creation of smart amber jewelry. By integrating nanosensors into the amber, it can be transformed into a wearable device thatcan monitor various health parameters, such as heart rateor body temperature. This would not only add a unique functionality to amber jewelry but also contribute to the advancement of wearable technology.In conclusion, nanotechnology has the potential to greatly enhance the beauty, durability, and functionalityof amber jewelry. By manipulating nanoparticles, amber canbe made more visually appealing, durable, and even possess self-cleaning properties. Furthermore, the integration of nanosensors can transform amber into a smart jewelry piece. With all these potential benefits, it is clear that nanotechnology can revolutionize the use of amber in the jewelry industry.中文回答：纳米技术是一个快速发展的领域，有潜力改变各个行业，包括珠宝业。

光子晶体导波基本原理说明书

More informationFundamentals of Photonic Crystal GuidingIf you’re looking to understand photonic crystals,this systematic,rigorous,and peda-gogical introduction is a must.Here you’llﬁnd intuitive analytical and semi-analyticalmodels applied to complex and practically relevant photonic crystal structures.Y ou willalso be shown how to use various analytical methods borrowed from quantum mechanics,such as perturbation theory,asymptotic analysis,and group theory,to investigate manyof the limiting properties of photonic crystals,which are otherwise difﬁcult to rationalizeusing only numerical simulations.An introductory review of nonlinear guiding in photonic lattices is also presented,as are the fabrication and application of photonic crystals.In addition,end-of-chapterexercise problems with detailed analytical and numerical solutions allow you to monitoryour understanding of the material presented.This accessible text is ideal for researchersand graduate students studying photonic crystals in departments of electrical engineering,physics,applied physics,and mathematics.Maksim Skorobogatiy is Professor and Canada Research Chair in Photonic Crystals atthe Department of Engineering Physics in´Ecole Polytechnique de Montr´e al,Canada.In2005he was awarded a fellowship from the Japanese Society for Promotion of Science,and he is a member of the Optical Society of America.Jianke Yang is Professor of Applied Mathematics at the University of Vermont,USA.Heis a member of the Optical Society of America and the Society of Industrial and AppliedMathematics.Fundamentals of Photonic Crystal GuidingMAKSIM SKOROBOGATIY 1JIANKE YANG 2´Ecole Polytechnique de Montr ´e al,Canada 1University of Vermont,USA2More informationMore informationcambridge university pressCambridge,New Y ork,Melbourne,Madrid,Cape Town,Singapore,S˜a o Paulo,DelhiCambridge University PressThe Edinburgh Building,Cambridge CB28RU,UKPublished in the United States of America by Cambridge University Press,New Y orkInformation on this title:/9780521513289C Cambridge University Press2009This publication is in copyright.Subject to statutory exceptionand to the provisions of relevant collective licensing agreements,no reproduction of any part may take place withoutthe written permission of Cambridge University Press.First published2009Printed in the United Kingdom at the University Press,CambridgeA catalog record for this publication is available from the British LibraryLibrary of Congress Cataloging in Publication dataSkorobogatiy,Maksim,1974–Fundamentals of photonic crystal guiding/by Maksim Skorobogatiy and Jianke Y ang.p.cm.Includes index.ISBN978-0-521-51328-91.Photonic crystals.I.Y ang,Jianke.II.Title.QD924.S562008621.36–dc222008033576ISBN978-0-521-51328-9hardbackCambridge University Press has no responsibility for the persistence oraccuracy of URLs for external or third-party internet websites referred toin this publication,and does not guarantee that any content on suchwebsites is,or will remain,accurate or appropriate.More informationM.Skorobogatiy dedicates this book to his family.He thanks his parentsAlexander and Tetyana for never-ceasing support,encouragement,andparticipation in all his endeavors.He also thanks his wife Olga,his children,Alexander junior and Anastasia,andhis parents for their unconditional love.J.Yang dedicates this book to his family.More informationContentsPreface page xiAcknowledgements xii1Introduction11.1Fabrication of photonic crystals21.2Application of photonic crystals41.2.1Photonic crystals as low-loss mirrors:photonicbandgap effects41.2.2Photonic crystals for out-of-bandgap operation10References112Hamiltonian formulation of Maxwell’s equations(frequency consideration)142.1Plane-wave solution for uniform dielectrics162.2Methods of quantum mechanics in electromagnetism182.2.1Orthogonality of eigenstates192.2.2Variational principle202.2.3Equivalence between the eigenstates of twocommuting Hamiltonians222.2.4Eigenstates of the operators of continuous anddiscrete translations and rotations232.3Properties of the harmonic modes of Maxwell’s equations302.3.1Orthogonality of electromagnetic modes322.3.2Eigenvalues and the variational principle322.3.3Absence of the fundamental length scale in Maxwell’sequations342.4Symmetries of electromagnetic eigenmodes352.4.1Time-reversal symmetry352.4.2Deﬁnition of the operators of translation and rotation352.4.3Continuous translational and rotational symmetries382.4.4Band diagrams432.4.5Discrete translational and rotational symmetries44More informationviii Contents2.4.6Discrete translational symmetry and discreterotational symmetry522.4.7Inversion symmetry,mirror symmetry,and other symmetries532.5Problems553One-dimensional photonic crystals–multilayer stacks593.1Transfer matrix technique593.1.1Multilayer stack,TE polarization593.1.2Multilayer stack,TM polarization613.1.3Boundary conditions623.2Reﬂection from aﬁnite multilayer(dielectric mirror)633.3Reﬂection from a semi-inﬁnite multilayer(dielectricphotonic crystal mirror)643.3.1Omnidirectional reﬂectors I683.4Guiding in aﬁnite multilayer(planar dielectric waveguide)693.5Guiding in the interior of an inﬁnitely periodic multilayer703.5.1Omnidirectional reﬂectors II803.6Defect states in a perturbed periodic multilayer:planarphotonic crystal waveguides823.7Problems864Bandgap guidance in planar photonic crystal waveguides934.1Design considerations of waveguides with inﬁnitelyperiodic reﬂectors934.2Fundamental TE mode of a waveguide with inﬁnitelyperiodic reﬂector964.3Inﬁnitely periodic reﬂectors,ﬁeld distribution in TM modes984.3.1Case of the core dielectric constantεc<εhεl/(εh+εl)984.3.2Case of the core dielectric constantεl≥εc>εhεl/(εh+εl)1014.4Perturbation theory for Maxwell’s equations,frequencyformulation1034.4.1Accounting for the absorption losses of the waveguidematerials:calculation of the modal lifetime and decay length1044.5Perturbative calculation of the modal radiation loss in aphotonic bandgap waveguide with aﬁnite reﬂector1064.5.1Physical approach1064.5.2Mathematical approach1085Hamiltonian formulation of Maxwell’s equations for waveguides(propagation-constant consideration)1105.1Eigenstates of a waveguide in Hamiltonian formulation1105.1.1Orthogonality relation between the modes of a waveguide madeof lossless dielectrics111More informationContents ix5.1.2Expressions for the modal phase velocity1145.1.3Expressions for the modal group velocity1145.1.4Orthogonality relation between the modes of a waveguide madeof lossy dielectrics1155.2Perturbation theory for uniform variations in a waveguide dielectric proﬁle1165.2.1Perturbation theory for the nondegenerate modes:example ofmaterial absorption1185.2.2Perturbation theory for the degenerate modes coupled byperturbation:example of polarization-mode dispersion1205.2.3Perturbations that change the positions of dielectric interfaces1235.3Problems126References127 6Two-dimensional photonic crystals1296.1T wo-dimensional photonic crystals with diminishingly smallindex contrast1296.2Plane-wave expansion method1326.2.1Calculation of the modal group velocity1346.2.2Plane-wave method in2D1346.2.3Calculation of the group velocity in the case of2Dphotonic crystals1356.2.4Perturbative formulation for the photonic crystallattices with small refractive index contrast1386.2.5Photonic crystal lattices with high-refractive-index contrast1426.3Comparison between various projected band diagrams1426.4Dispersion relation at a band edge,density of states andVan Hove singularities1446.5Refraction from photonic crystals1476.6Defects in a2D photonic crystal lattice1486.6.1Line defects1486.6.2Point defects1586.7Problems167References171 7Quasi-2D photonic crystals1727.1Photonic crystalﬁbers1727.1.1Plane-wave expansion method1727.1.2Band diagram of modes of a photonic crystalﬁber1767.2Optically induced photonic lattices1777.2.1Light propagation in low-index-contrast periodicphotonic lattices1787.2.2Defect modes in2D photonic lattices with localized defects1817.2.3Bandgap structure and diffraction relation for the modes of auniform lattice182More informationx Contents7.2.4Bifurcations of the defect modes from Bloch band edges forlocalized weak defects1857.2.5Dependence of the defect modes on the strength oflocalized defects1887.2.6Defect modes in2D photonic lattices with nonlocalized defects1927.3Photonic-crystal slabs1957.3.1Geometry of a photonic-crystal slab1957.3.2Eigenmodes of a photonic-crystal slab1977.3.3Analogy between the modes of a photonic-crystal slab and themodes of a corresponding2D photonic crystal2007.3.4Modes of a photonic-crystal slab waveguide2047.4Problems207References208 8Nonlinear effects and gap–soliton formation in periodic media2108.1Solitons bifurcated from Bloch bands in1D periodic media2118.1.1Bloch bands and bandgaps2118.1.2Envelope equations of Bloch modes2128.1.3Locations of envelope solitons2158.1.4Soliton families bifurcated from band edges2168.2Solitons bifurcated from Bloch bands in2D periodic media2188.2.1T wo-dimensional Bloch bands and bandgaps of linearperiodic systems2198.2.2Envelope equations of2D Bloch modes2208.2.3Families of solitons bifurcated from2D band edges2238.3Soliton families not bifurcated from Bloch bands2268.4Problems227References228Problem solutions230Chapter2230Chapter3236Chapter5244Chapter6246Chapter7257Chapter8260 Index263More informationPrefaceTheﬁeld of photonic crystals(aka periodic photonic structures)is experiencing anunprecedented growth due to the dramatic ways in which such structures can control,modify,and harvest theﬂow of light.The idea of writing this book came to M.Skorobogatiy when he was developingan introductory course on photonic crystals at the Ecole Polytechnique de Montr´e al/University of Montr´e al.Theﬁeld of photonic crystals,being heavily dependent onnumerical simulations,is somewhat challenging to introduce without sacriﬁcing thequalitative understanding of the underlying physics.On the other hand,exactly solvablemodels,where the relation between physics and quantitative results is most transpar-ent,only exist for photonic crystals of trivial geometries.The challenge,therefore,wasto develop a presentational approach that would maximally use intuitive analytical andsemi-analytical models,while applying them to complex and practically relevant pho-tonic crystal structures.We would like to note that the main purpose of this book is not to present the latestadvancements in theﬁeld of photonic crystals,but rather to give a systematic,logical,andpedagogical introduction to this vibrantﬁeld.The text is largely aimed at students andresearchers who want to acquire a rigorous,while intuitive,mathematical introductioninto the subject of guided modes in photonic crystals and photonic crystal waveguides.The text,therefore,favors analysis of analytically or semi-analytically solvable problemsover pure numerical modeling.We believe that this is a more didactical approach whentrying to introduce a novice into a newﬁeld.To further stimulate understanding of thebook content,we suggest many exercise problems of physical relevance that can besolved analytically.In the course of the book we extensively use the analogy between the Hamiltonian for-mulation of Maxwell’s equations and the Hamiltonian formulation of quantum mechan-ics.We present both frequency and propagation-constant based Hamiltonian formula-tions of Maxwell’s equations.The latter is particularly useful for analyzing photoniccrystal-based linear and nonlinear waveguides andﬁbers.This approach allows us touse a well-developed machinery of quantum mechanical semi-analytical methods,suchas perturbation theory,asymptotic analysis,and group theory,to investigate many ofthe limiting properties of photonic crystals,which are otherwise difﬁcult to investigatebased only on numerical simulations.M.Skorobogatiy has contributed Chapters2,3,4,5,and6of this book,and J.Y anghas contributed Chapter8.Chapters1and7were co-authored by both authors.More informationAcknowledgementsM.Skorobogatiy would like to thank his graduate and postgraduate program mentors,Professor J.D.Joannopoulos and Professor Y.Fink from MIT,for introducing him intotheﬁeld of photonic crystals.He is grateful to Professor M.Koshiba and ProfessorK.Saitoh for hosting him at Hokkaido University in2005and for having many excitingdiscussions in the area of photonic crystalﬁbers.M.Skorobogatiy acknowledges theCanada Research Chair program for making this book possible by reducing his teachingload.J.Y ang thanks the funding support of the US Air Force Ofﬁce of Scientiﬁc Research,which made many results of this book possible.He also thanks the Zhou Pei-Yuan Centerfor Applied Mathematics at Tsinghua University(China)for hospitality during his visit,where portions of this book were written.Both authors are grateful to their graduate andpostgraduate students for their comments and help,while this book was in preparation.Especially,J.Y ang likes to thank Dr.Jiandong Wang,whose help was essential for hisbook writing.。

炼金术文化史英文版译本

炼金术文化史英文版译本The History of Alchemy CultureAlchemy, an ancient practice rooted in mysticism and science, has held a prominent place in human civilization for centuries. Its rich history spans across continents and has left a lasting impact on the development of various cultures. Exploring the evolution of alchemy and its cultural significance unlocks a fascinating world of knowledge, symbolism, and transformation.The origins of alchemy can be traced back to ancient civilizations in Egypt, Greece, and China. In each culture, alchemy developed independently, driven by the quest to understand the nature of matter and the secrets of the universe. These early alchemists sought to transmute base metals into gold, believing that such a feat would unlock spiritual and material perfection.Alchemy's importance in Egyptian culture is evident in the myths and legends that surround it. The story of Isis and Osiris, for example, echoes the alchemical process of death and rebirth, symbolizing the transformation of the soul. Egyptian alchemists also engaged in the practice ofmummification, which can be seen as an early form ofpreserving the body in the hopes of achieving immortality.In ancient Greece, the work of philosophers such as Pythagoras and Heraclitus contributed to the development of alchemical theories. Their ideas about the fundamental elements of the universe, such as earth, air, fire, and water, laid the groundwork for alchemical practices. Greek alchemists, like their Egyptian counterparts, sought not only to transform metals but also to purify the soul and attain spiritual enlightenment.In China, alchemy manifested as a combination of Taoism and traditional Chinese medicine. The concepts of yin and yang, qi, and the five elements influenced alchemical theories, which aimed at achieving physical immortality. Chinese alchemists explored the elixir of life, a substance that would grant longevity and transcendence. Additionally,the search for the philosopher's stone, a mythical substance capable of turning base metals into gold, drove Chinese alchemical endeavors.During the Middle Ages, alchemy made its way to Europe, where it became intertwined with mystical and religious beliefs. Amid the Christian dominance, alchemical symbolism merged with Christian motifs, resulting in a complex andesoteric system. Alchemists, known as "philosophers of fire," believed that the transmutation of metals was an allegory for the spiritual transformation of the soul.The Renaissance marked a turning point for alchemy, as it transitioned from more metaphorical and spiritual pursuits to a more scientific approach. Influential figures like Paracelsus and Isaac Newton contributed to the advancement of chemistry while building upon alchemical principles. However, as alchemy embraced empirical methods, it gradually transformed into what we now know as modern chemistry, leaving behind its mystical and symbolic aspects.Despite its transformation into modern science, alchemy's influence can still be seen in various aspects of contemporary culture. Its symbolism and concepts continue to inspire artists, writers, and thinkers who seek to explore the depths of human existence and transformation. The alchemical process serves as a metaphor for personal growth and the pursuit of knowledge, reminding us that life is a constant journey of change and discovery.In conclusion, the history of alchemy is a testament to the enduring human fascination with transformation and understanding the secrets of the universe. From its ancient origins in Egypt, Greece, and China to its evolution duringthe Middle Ages and Renaissance, alchemy has shaped the cultural landscapes of numerous civilizations. Its legacy, deeply intertwined with spirituality and science, continues to inspire and guide seekers of wisdom and enlightenment.。

英文诗歌鉴赏对比研究-夜莺颂（济慈）和我孤独地漫游-像一朵云（华兹华斯）

IntroductionThe names Wordsworth and Keats are to a certain extent tantamount to Romanticism, especially from the perspective of modern academics.John Keats's "Ode to a Nightingale" and William Wordsworth's "I wandered lonely as a cloud" seem to have been written with the intention of describing a moment in one's life, like that of the fleeting tune of a nightingale or the discovery of a field of daffodils by a lake. Within each of these moments a multitude of emotions are established, with each morphing from one to another very subtly. What are also more subtle about these two poems are their differences. While they do touch on very similar topics, the objects used to personify Keats' ideas on death and immortality differs from Wordsworth's ideas on an inherent unity between man and nature. Thus, the ideas represented by them do diverge at different points in the poems as well.Comparison of John Keats's "Ode to a Nightingale" and William Wordsworth's "I wandered lonely as a cloud"JohnKeats uses this beauty to create a central theme in one of his prominent poems, "Ode to a Nightingale". The beauty in "Ode to a Nightingale" is that of the Nightingale's song. The beautiful song of the nightingale is reminding the poet of his own mortality by singing to his senses. It is the beauty that he sees in the world which makes it apparent that society is destined to perish and die. Keats shows the deepest expression of human mortality in this poem as he discusses the relationship to mature age and how it compares to the fluid song of the Nightingale. The man in the poem longs to flee from the world he lives and join the bird in its world.Keats's symbolism of the Nightingale and the contrast between life and death reveals his changing view of life resulting in the belief of death being his means to overcome pain. Keats begins this revelation by describing the beauty of life, but his use of fantasy words foreshadows a change in his outlook. By using the symbolism of the nightingale, Keats becomes uncertain of his view of life and begins to ponder theconcept of death. In the conclusion, Keats feels deceived by the nightingale's representation of life, and desires death to overcome his pain instead of enduring it in life.As Keats continues his thoughts, he becomes more and more skeptical of life. Fascinated by the nightingale, Keats recognizes the bird's innocence: "What thou among the leaves hast never known, /The weariness, The fever, and the fret". One would fret when uneasy or uncertain towards a matter. Keats reveals that the nightingale is oblivious to the concept of death as it sings its melody. The nightingale is completely free for it does not know about death. Keats becomes tormented by the innocence and freedom of the bird, as all of Keats' uncertainties regarding life and death overwhelm him: "Where but to think is to be full of sorrow". Living his life brings a constant reminder of his pain, driving Keats to change his opinion of life and death.Similarly, as a great poet of nature, William Wordsworth wrote many famous poems to express his love for nature, one of which is "I wandered lonely as a cloud". In the narrative poem, the poet successfully compared his loneliness with the happy and vital daffodils. The daffodils, the symbol of the nature, bring great joy and relief to the speaker. So Wordsworth's conception of nature is that nature has a lot to do with man, it can not only refresh one's soul and fill one with happiness, but it can also be reduced into a beautiful memory which will comfort one's heart when in solitude.I chose the poem "I wandered lonely as a cloud" by William Wordsworth because I like the imagery in it of dancing daffodils. Upon closer examination, I realized that most of this imagery is created by the many metaphors and similes Wordsworth uses. In the first line, Wordsworth says "I wandered lonely as a cloud". This is a simile comparing the wondering of a man to a cloud drifting through the sky.I suppose the wandering cloud is lonely because there is nothing up there that high in the sky besides it. It can pass by unnoticed, touching nothing. Also, the image of a cloud brings to mind a light, carefree sort of wandering. The cloud is not bound by any obstacle, but can go wherever the whim of the wind takes it.This simple poem, one of the loveliest and most famous in the Wordsworthcanon, revisits the familiar subjects of nature and memory, this time with a particularly (simple) spare, musical eloquence. The plot is extremely simple, depicting the poet's wandering and his discovery of a field of daffodils by a lake, the memory of which pleases him and comforts him when he is lonely, bored, or restless. Romantic poet William Wordsworth's "I Wandered Lonely as a Cloud" extols the virtue of nature and highlights the value of participating in its beauty.ConclusionIn "Ode to a Nightingale" and" I wandered lonely as a cloud ", both poems tells of an experience in which the human characters encounters nature in the poems, and the experiences are handled quite differently in the two poems. Natures have always held significance in human lives. They achieved heights unattainable to humans and sung while they did that. These two poets use nature as their muse and also symbolically for the human experience. The two poems, "Ode to a Nightingale" and "I wandered lonely as a cloud", clearly portray both of the poets' treatment on the idea of escape.Both poems construct vivid illusions but insist on their desolating failure. The poems do seem similar in several ways because in both, Keats and Wordsworth do portray symbols of realism while depicting the nature, as well as the spectrum of emotions from grief to joy. The central themes of the two poems are neither a nightingale nor a daffodil, but, the poets' eternal search for a center of refuge in a world of flux. It is through such a conception that Keats and Wordsworth sets to resolve the dichotomy between the world of the ideal and that of reality within the order of experience.Reference[1]Plumly, Stanley.: "The immortal evening: a legendary dinner with Keats, Wordsworth, and Lamb." New Y ork; London: Norton, 2014. pp. 368. (2014)[2]Lau, Beth.: review of Stillinger, Jack. "Romantic complexity: Keats, Coleridge, and Wordsworth." Studies in Romanticism (47:3) 2008, 420-5. (2008)[3]Horrell, William C.: review of Milnes, Tim. "The truth about Romanticism: pragmatism and idealism in Keats, Shelley,Wordsworth and Coleridge."Wordsworth Circle (42:4) 2011, 266-9. (2011)[4]Burkett, Andrew.: review of Roe, Nicholas. "John Keats: a new life." Studies in Romanticism (54:1) 2015, 138-42. (2015)[5]Michael, Timothy.: review of Milnes, Tim. "The truth about Romanticism: pragmatism and idealism in Keats, Shelley, Coleridge." Romanticism (19:1) 2013, 101-3. (2013)[6]Scott, Matthew.: "Wordsworth among the Romantics." In (pp. 749-66) Gravil, Richard; Robinson, Daniel (eds). The Oxford handbook of William Wordsworth. Oxford; New Y ork: [2015:458328]. (2015)[7] Wu, Duncan.: "Wordsworth and sensibility." In (pp. 467-81) Gravil, Richard; Robinson, Daniel (eds). The Oxford handbook of William Wordsworth. Oxford; New Y ork [2015:458328]. (2015)。

想要了解的事物英语作文

想要了解的事物英语作文There are so many things in this world that I want to understand better. From the smallest particles that make up the universe to the grandest mysteries of the cosmos, the sheer vastness of human knowledge and the unknown is both humbling and exhilarating. Every day, new discoveries are being made that expand the boundaries of what we know, and I find myself constantly in awe of the incredible complexity and beauty of our reality.One of the areas I'm most fascinated by is the field of quantum physics. The counterintuitive behaviors of subatomic particles, like the fact that they can exist in multiple states simultaneously, have always captivated me. I would love to gain a deeper understanding of concepts like quantum entanglement, wave-particle duality, and the uncertainty principle. How can particles that are separated by vast distances instantly influence each other? What is the true nature of reality at the most fundamental level? These are the kinds of questions that keep me up at night, pondering the very fabric of existence.At the same time, I'm also deeply interested in the workings of the human mind and consciousness. How do our brains process information and give rise to the rich inner experience of thoughts, emotions, and sensations? What is the relationship between the physical brain and the subjective self? The field of neuroscience has made incredible strides in mapping the neural pathways and mechanisms underlying various cognitive functions, but there is still so much we don't understand about the emergent phenomenon of consciousness.I'm also endlessly curious about the origins and evolution of life on our planet. How did the first self-replicating molecules arise from the primordial soup, and what were the key evolutionary steps that led to the incredible diversity of life we see today? What are the fundamental principles and mechanisms that drive the evolution of species, and how do they interact with the ever-changing environment? The more I learn about biology and the history of life, the more I realize how little we truly know about the origins and mechanics of the living world.Another area that fascinates me is the vastness of the cosmos and our place within it. The scale of the universe, with its billions of galaxies separated by unimaginable distances, is almost incomprehensible to the human mind. What is the true nature of space and time? How did the universe begin, and what is its ultimatefate? Will we ever unravel the mysteries of dark matter and dark energy, the enigmatic components that seem to make up the majority of the universe? The more we learn, the more questions arise, and I'm driven to understand our place in this grand cosmic tapestry.Of course, there are also countless aspects of the human experience that I wish I could understand better. What are the roots of human behavior, and how do our evolutionary and cultural histories shape the way we think and act? How do we form meaningful connections with others, and what are the psychological and neurological underpinnings of love, empathy, and social bonds? What is the nature of consciousness, and how do subjective experiences emerge from the physical brain? These are the kinds of deep, existential questions that captivate me and drive my curiosity.Ultimately, I believe that the pursuit of knowledge and understanding is one of the most noble and rewarding endeavors a human being can undertake. The more we learn about the world and the universe around us, the more we realize how much we still have to discover. And with each new insight, we gain a deeper appreciation for the incredible complexity and beauty of our reality. It is a never-ending journey of exploration and discovery, and I am honored to be a part of it. There is simply so much I want tounderstand, and I can't wait to continue on this wondrous path of learning and growth.。

《真正的英雄》翻译问题评析修改稿

《真正的英雄》翻译问题评析韩孟奇（华北水利水电学院外国语学院，河南郑州450011）摘要：以《真正的英雄》为例，指出了译文在原文理解、词语搭配、人称代词处理、术语和专有名词翻译、表达、人名翻译方面存在的问题，对一些问题进行了定量和定性分析，并就问题的解决提出了建议。

关键词：词语搭配；人称代词；术语和专有名词；翻译腔；人名翻译中途分类号：H059引言《真正的英雄》为义务教育课程标准试验教科书《语文》七年级下册（2009）第24课课文，是一篇选自辽宁人民出版社《世界名人演说经典》的译文，其原文出自美国前总统里根(Ronald Reagan) 哀悼挑战者号航天飞机失事的演讲(In Memory of the Challenger Astronauts)。

作为由课程教材研究所和中学语文课程教材研究开发中心编著、人民教育出版社出版的中学语文教材，其选材要求不可谓不严。

但浏览一下译文，就会发现诸多问题，再对照原文细看，感觉问题更加严重。

该教材面向全国发行，其传播力与影响力不容小觑，有必要藉此探讨，引起出版单位的注意，对译文重新校对，及早纠正，以免造成不良影响。

1.0 存在问题译文所暴露的主要问题有误读原文、词语搭配不当、人称代词处理不当、术语和专有名词翻译不当、翻译腔、人名翻译不规范等。

1.1误读原文正确理解原文是翻译的关键，如果误读、曲解或理解不透彻，这些问题势必会暴露在翻译中。

《真正的英雄》一文存在多处由于误读原文而引起的翻译错误，如：1) 原译：我们也不会忘记孩提时总爱光着脚板在咖啡地和夏威夷的麦卡达美亚墓地跑来跑去的埃里森•奥尼佐卡，他早就梦想有一天去月球旅行。

一个光脚丫的孩子在墓地跑来跑去，这会在中学生的脑海里产生什么样的意象呢？语文老师又如何解释这一现象呢？笔者没做过调查，不敢妄言，但在阅读译文时，除了不知所云，还有点惊悚的感觉。

刚开始还以为是“文化冲击”(culture shock)，细读原文，真相原来如此，与译文可谓是南辕北辙。

毕业设计论文塑料注射成型

Modeling of morphology evolution in the injection moldingprocess of thermoplastic polymersR.Pantani,I.Coccorullo,V.Speranza,G.Titomanlio* Department of Chemical and Food Engineering,University of Salerno,via Ponte don Melillo,I-84084Fisciano(Salerno),Italy Received13May2005;received in revised form30August2005;accepted12September2005AbstractA thorough analysis of the effect of operative conditions of injection molding process on the morphology distribution inside the obtained moldings is performed,with particular reference to semi-crystalline polymers.The paper is divided into two parts:in the ﬁrst part,the state of the art on the subject is outlined and discussed;in the second part,an example of the characterization required for a satisfactorily understanding and description of the phenomena is presented,starting from material characterization,passing through the monitoring of the process cycle and arriving to a deep analysis of morphology distribution inside the moldings.In particular,fully characterized injection molding tests are presented using an isotactic polypropylene,previously carefully characterized as far as most of properties of interest.The effects of both injectionﬂow rate and mold temperature are analyzed.The resulting moldings morphology(in terms of distribution of crystallinity degree,molecular orientation and crystals structure and dimensions)are analyzed by adopting different experimental techniques(optical,electronic and atomic force microscopy,IR and WAXS analysis).Final morphological characteristics of the samples are compared with the predictions of a simulation code developed at University of Salerno for the simulation of the injection molding process.q2005Elsevier Ltd.All rights reserved.Keywords:Injection molding;Crystallization kinetics;Morphology;Modeling;Isotactic polypropyleneContents1.Introduction (1186)1.1.Morphology distribution in injection molded iPP parts:state of the art (1189)1.1.1.Modeling of the injection molding process (1190)1.1.2.Modeling of the crystallization kinetics (1190)1.1.3.Modeling of the morphology evolution (1191)1.1.4.Modeling of the effect of crystallinity on rheology (1192)1.1.5.Modeling of the molecular orientation (1193)1.1.6.Modeling of theﬂow-induced crystallization (1195)ments on the state of the art (1197)2.Material and characterization (1198)2.1.PVT description (1198)*Corresponding author.Tel.:C39089964152;fax:C39089964057.E-mail address:gtitomanlio@unisa.it(G.Titomanlio).2.2.Quiescent crystallization kinetics (1198)2.3.Viscosity (1199)2.4.Viscoelastic behavior (1200)3.Injection molding tests and analysis of the moldings (1200)3.1.Injection molding tests and sample preparation (1200)3.2.Microscopy (1202)3.2.1.Optical microscopy (1202)3.2.2.SEM and AFM analysis (1202)3.3.Distribution of crystallinity (1202)3.3.1.IR analysis (1202)3.3.2.X-ray analysis (1203)3.4.Distribution of molecular orientation (1203)4.Analysis of experimental results (1203)4.1.Injection molding tests (1203)4.2.Morphology distribution along thickness direction (1204)4.2.1.Optical microscopy (1204)4.2.2.SEM and AFM analysis (1204)4.3.Morphology distribution alongﬂow direction (1208)4.4.Distribution of crystallinity (1210)4.4.1.Distribution of crystallinity along thickness direction (1210)4.4.2.Crystallinity distribution alongﬂow direction (1212)4.5.Distribution of molecular orientation (1212)4.5.1.Orientation along thickness direction (1212)4.5.2.Orientation alongﬂow direction (1213)4.5.3.Direction of orientation (1214)5.Simulation (1214)5.1.Pressure curves (1215)5.2.Morphology distribution (1215)5.3.Molecular orientation (1216)5.3.1.Molecular orientation distribution along thickness direction (1216)5.3.2.Molecular orientation distribution alongﬂow direction (1216)5.3.3.Direction of orientation (1217)5.4.Crystallinity distribution (1217)6.Conclusions (1217)References (1219)1.IntroductionInjection molding is one of the most widely employed methods for manufacturing polymeric products.Three main steps are recognized in the molding:ﬁlling,packing/holding and cooling.During theﬁlling stage,a hot polymer melt rapidlyﬁlls a cold mold reproducing a cavity of the desired product shape. During the packing/holding stage,the pressure is raised and extra material is forced into the mold to compensate for the effects that both temperature decrease and crystallinity development determine on density during solidiﬁcation.The cooling stage starts at the solidiﬁcation of a thin section at cavity entrance (gate),starting from that instant no more material can enter or exit from the mold impression and holding pressure can be released.When the solid layer on the mold surface reaches a thickness sufﬁcient to assure required rigidity,the product is ejected from the mold.Due to the thermomechanical history experienced by the polymer during processing,macromolecules in injection-molded objects present a local order.This order is referred to as‘morphology’which literally means‘the study of the form’where form stands for the shape and arrangement of parts of the object.When referred to polymers,the word morphology is adopted to indicate:–crystallinity,which is the relative volume occupied by each of the crystalline phases,including mesophases;–dimensions,shape,distribution and orientation of the crystallites;–orientation of amorphous phase.R.Pantani et al./Prog.Polym.Sci.30(2005)1185–1222 1186R.Pantani et al./Prog.Polym.Sci.30(2005)1185–12221187Apart from the scientiﬁc interest in understandingthe mechanisms leading to different order levels inside a polymer,the great technological importance of morphology relies on the fact that polymer character-istics (above all mechanical,but also optical,electrical,transport and chemical)are to a great extent affected by morphology.For instance,crystallinity has a pro-nounced effect on the mechanical properties of the bulk material since crystals are generally stiffer than amorphous material,and also orientation induces anisotropy and other changes in mechanical properties.In this work,a thorough analysis of the effect of injection molding operative conditions on morphology distribution in moldings with particular reference to crystalline materials is performed.The aim of the paper is twofold:ﬁrst,to outline the state of the art on the subject;second,to present an example of the characterization required for asatisfactorilyR.Pantani et al./Prog.Polym.Sci.30(2005)1185–12221188understanding and description of the phenomena, starting from material description,passing through the monitoring of the process cycle and arriving to a deep analysis of morphology distribution inside the mold-ings.To these purposes,fully characterized injection molding tests were performed using an isotactic polypropylene,previously carefully characterized as far as most of properties of interest,in particular quiescent nucleation density,spherulitic growth rate and rheological properties(viscosity and relaxation time)were determined.The resulting moldings mor-phology(in terms of distribution of crystallinity degree, molecular orientation and crystals structure and dimensions)was analyzed by adopting different experimental techniques(optical,electronic and atomic force microscopy,IR and WAXS analysis).Final morphological characteristics of the samples were compared with the predictions of a simulation code developed at University of Salerno for the simulation of the injection molding process.The effects of both injectionﬂow rate and mold temperature were analyzed.1.1.Morphology distribution in injection molded iPP parts:state of the artFrom many experimental observations,it is shown that a highly oriented lamellar crystallite microstructure, usually referred to as‘skin layer’forms close to the surface of injection molded articles of semi-crystalline polymers.Far from the wall,the melt is allowed to crystallize three dimensionally to form spherulitic structures.Relative dimensions and morphology of both skin and core layers are dependent on local thermo-mechanical history,which is characterized on the surface by high stress levels,decreasing to very small values toward the core region.As a result,the skin and the core reveal distinct characteristics across the thickness and also along theﬂow path[1].Structural and morphological characterization of the injection molded polypropylene has attracted the interest of researchers in the past three decades.In the early seventies,Kantz et al.[2]studied the morphology of injection molded iPP tensile bars by using optical microscopy and X-ray diffraction.The microscopic results revealed the presence of three distinct crystalline zones on the cross-section:a highly oriented non-spherulitic skin;a shear zone with molecular chains oriented essentially parallel to the injection direction;a spherulitic core with essentially no preferred orientation.The X-ray diffraction studies indicated that the skin layer contains biaxially oriented crystallites due to the biaxial extensionalﬂow at theﬂow front.A similar multilayered morphology was also reported by Menges et al.[3].Later on,Fujiyama et al.[4] investigated the skin–core morphology of injection molded iPP samples using X-ray Small and Wide Angle Scattering techniques,and suggested that the shear region contains shish–kebab structures.The same shish–kebab structure was observed by Wenig and Herzog in the shear region of their molded samples[5].A similar investigation was conducted by Titomanlio and co-workers[6],who analyzed the morphology distribution in injection moldings of iPP. They observed a skin–core morphology distribution with an isotropic spherulitic core,a skin layer characterized by aﬁne crystalline structure and an intermediate layer appearing as a dark band in crossed polarized light,this layer being characterized by high crystallinity.Kalay and Bevis[7]pointed out that,although iPP crystallizes essentially in the a-form,a small amount of b-form can be found in the skin layer and in the shear region.The amount of b-form was found to increase by effect of high shear rates[8].A wide analysis on the effect of processing conditions on the morphology of injection molded iPP was conducted by Viana et al.[9]and,more recently, by Mendoza et al.[10].In particular,Mendoza et al. report that the highest level of crystallinity orientation is found inside the shear zone and that a high level of orientation was also found in the skin layer,with an orientation angle tilted toward the core.It is rather difﬁcult to theoretically establish the relationship between the observed microstructure and processing conditions.Indeed,a model of the injection molding process able to predict morphology distribution in theﬁnal samples is not yet available,even if it would be of enormous strategic importance.This is mainly because a complete understanding of crystallization kinetics in processing conditions(high cooling rates and pressures,strong and complexﬂowﬁelds)has not yet been reached.In this section,the most relevant aspects for process modeling and morphology development are identiﬁed. In particular,a successful path leading to a reliable description of morphology evolution during polymer processing should necessarily pass through:–a good description of morphology evolution under quiescent conditions(accounting all competing crystallization processes),including the range of cooling rates characteristic of processing operations (from1to10008C/s);R.Pantani et al./Prog.Polym.Sci.30(2005)1185–12221189–a description capturing the main features of melt morphology(orientation and stretch)evolution under processing conditions;–a good coupling of the two(quiescent crystallization and orientation)in order to capture the effect of crystallinity on viscosity and the effect ofﬂow on crystallization kinetics.The points listed above outline the strategy to be followed in order to achieve the basic understanding for a satisfactory description of morphology evolution during all polymer processing operations.In the following,the state of art for each of those points will be analyzed in a dedicated section.1.1.1.Modeling of the injection molding processTheﬁrst step in the prediction of the morphology distribution within injection moldings is obviously the thermo-mechanical simulation of the process.Much of the efforts in the past were focused on the prediction of pressure and temperature evolution during the process and on the prediction of the melt front advancement [11–15].The simulation of injection molding involves the simultaneous solution of the mass,energy and momentum balance equations.Theﬂuid is non-New-tonian(and viscoelastic)with all parameters dependent upon temperature,pressure,crystallinity,which are all function of pressibility cannot be neglected as theﬂow during the packing/holding step is determined by density changes due to temperature, pressure and crystallinity evolution.Indeed,apart from some attempts to introduce a full 3D approach[16–19],the analysis is currently still often restricted to the Hele–Shaw(or thinﬁlm) approximation,which is warranted by the fact that most injection molded parts have the characteristic of being thin.Furthermore,it is recognized that the viscoelastic behavior of the polymer only marginally inﬂuences theﬂow kinematics[20–22]thus the melt is normally considered as a non-Newtonian viscousﬂuid for the description of pressure and velocity gradients evolution.Some examples of adopting a viscoelastic constitutive equation in the momentum balance equations are found in the literature[23],but the improvements in accuracy do not justify a considerable extension of computational effort.It has to be mentioned that the analysis of some features of kinematics and temperature gradients affecting the description of morphology need a more accurate description with respect to the analysis of pressure distributions.Some aspects of the process which were often neglected and may have a critical importance are the description of the heat transfer at polymer–mold interface[24–26]and of the effect of mold deformation[24,27,28].Another aspect of particular interest to the develop-ment of morphology is the fountainﬂow[29–32], which is often neglected being restricted to a rather small region at theﬂow front and close to the mold walls.1.1.2.Modeling of the crystallization kineticsIt is obvious that the description of crystallization kinetics is necessary if theﬁnal morphology of the molded object wants to be described.Also,the development of a crystalline degree during the process inﬂuences the evolution of all material properties like density and,above all,viscosity(see below).Further-more,crystallization kinetics enters explicitly in the generation term of the energy balance,through the latent heat of crystallization[26,33].It is therefore clear that the crystallinity degree is not only a result of simulation but also(and above all)a phenomenon to be kept into account in each step of process modeling.In spite of its dramatic inﬂuence on the process,the efforts to simulate the injection molding of semi-crystalline polymers are crude in most of the commercial software for processing simulation and rather scarce in the ﬂeur and Kamal[34],Papatanasiu[35], Titomanlio et al.[15],Han and Wang[36],Ito et al.[37],Manzione[38],Guo and Isayev[26],and Hieber [25]adopted the following equation(Kolmogoroff–Avrami–Evans,KAE)to predict the development of crystallinityd xd tZð1K xÞd d cd t(1)where x is the relative degree of crystallization;d c is the undisturbed volume fraction of the crystals(if no impingement would occur).A signiﬁcant improvement in the prediction of crystallinity development was introduced by Titoman-lio and co-workers[39]who kept into account the possibility of the formation of different crystalline phases.This was done by assuming a parallel of several non-interacting kinetic processes competing for the available amorphous volume.The evolution of each phase can thus be described byd x id tZð1K xÞd d c id t(2)where the subscript i stands for a particular phase,x i is the relative degree of crystallization,x ZPix i and d c iR.Pantani et al./Prog.Polym.Sci.30(2005)1185–1222 1190is the expectancy of volume fraction of each phase if no impingement would occur.Eq.(2)assumes that,for each phase,the probability of the fraction increase of a single crystalline phase is simply the product of the rate of growth of the corresponding undisturbed volume fraction and of the amount of available amorphous fraction.By summing up the phase evolution equations of all phases(Eq.(2))over the index i,and solving the resulting differential equation,one simply obtainsxðtÞZ1K exp½K d cðtÞ (3)where d c Z Pid c i and Eq.(1)is recovered.It was shown by Coccorullo et al.[40]with reference to an iPP,that the description of the kinetic competition between phases is crucial to a reliable prediction of solidiﬁed structures:indeed,it is not possible to describe iPP crystallization kinetics in the range of cooling rates of interest for processing(i.e.up to several hundreds of8C/s)if the mesomorphic phase is neglected:in the cooling rate range10–1008C/s, spherulite crystals in the a-phase are overcome by the formation of the mesophase.Furthermore,it has been found that in some conditions(mainly at pressures higher than100MPa,and low cooling rates),the g-phase can also form[41].In spite of this,the presence of different crystalline phases is usually neglected in the literature,essentially because the range of cooling rates investigated for characterization falls in the DSC range (well lower than typical cooling rates of interest for the process)and only one crystalline phase is formed for iPP at low cooling rates.It has to be noticed that for iPP,which presents a T g well lower than ambient temperature,high values of crystallinity degree are always found in solids which passed through ambient temperature,and the cooling rate can only determine which crystalline phase forms, roughly a-phase at low cooling rates(below about 508C/s)and mesomorphic phase at higher cooling rates.The most widespread approach to the description of kinetic constant is the isokinetic approach introduced by Nakamura et al.According to this model,d c in Eq.(1)is calculated asd cðtÞZ ln2ðt0KðTðsÞÞd s2 435n(4)where K is the kinetic constant and n is the so-called Avrami index.When introduced as in Eq.(4),the reciprocal of the kinetic constant is a characteristic time for crystallization,namely the crystallization half-time, t05.If a polymer is cooled through the crystallization temperature,crystallization takes place at the tempera-ture at which crystallization half-time is of the order of characteristic cooling time t q deﬁned ast q Z D T=q(5) where q is the cooling rate and D T is a temperature interval over which the crystallization kinetic constant changes of at least one order of magnitude.The temperature dependence of the kinetic constant is modeled using some analytical function which,in the simplest approach,is described by a Gaussian shaped curve:KðTÞZ K0exp K4ln2ðT K T maxÞ2D2(6)The following Hoffman–Lauritzen expression[42] is also commonly adopted:K½TðtÞ Z K0exp KUÃR$ðTðtÞK T NÞ!exp KKÃ$ðTðtÞC T mÞ2TðtÞ2$ðT m K TðtÞÞð7ÞBoth equations describe a bell shaped curve with a maximum which for Eq.(6)is located at T Z T max and for Eq.(7)lies at a temperature between T m(the melting temperature)and T N(which is classically assumed to be 308C below the glass transition temperature).Accord-ing to Eq.(7),the kinetic constant is exactly zero at T Z T m and at T Z T N,whereas Eq.(6)describes a reduction of several orders of magnitude when the temperature departs from T max of a value higher than2D.It is worth mentioning that only three parameters are needed for Eq.(6),whereas Eq.(7)needs the deﬁnition ofﬁve parameters.Some authors[43,44]couple the above equations with the so-called‘induction time’,which can be deﬁned as the time the crystallization process starts, when the temperature is below the equilibrium melting temperature.It is normally described as[45]Dt indDtZðT0m K TÞat m(8)where t m,T0m and a are material constants.It should be mentioned that it has been found[46,47]that there is no need to explicitly incorporate an induction time when the modeling is based upon the KAE equation(Eq.(1)).1.1.3.Modeling of the morphology evolutionDespite of the fact that the approaches based on Eq.(4)do represent a signiﬁcant step toward the descriptionR.Pantani et al./Prog.Polym.Sci.30(2005)1185–12221191of morphology,it has often been pointed out in the literature that the isokinetic approach on which Nakamura’s equation (Eq.(4))is based does not describe details of structure formation [48].For instance,the well-known experience that,with many polymers,the number of spherulites in the ﬁnal solid sample increases strongly with increasing cooling rate,is indeed not taken into account by this approach.Furthermore,Eq.(4)describes an increase of crystal-linity (at constant temperature)depending only on the current value of crystallinity degree itself,whereas it is expected that the crystallization rate should depend also on the number of crystalline entities present in the material.These limits are overcome by considering the crystallization phenomenon as the consequence of nucleation and growth.Kolmogoroff’s model [49],which describes crystallinity evolution accounting of the number of nuclei per unit volume and spherulitic growth rate can then be applied.In this case,d c in Eq.(1)is described asd ðt ÞZ C m ðt 0d N ðs Þd s$ðt sG ðu Þd u 2435nd s (9)where C m is a shape factor (C 3Z 4/3p ,for spherical growth),G (T (t ))is the linear growth rate,and N (T (t ))is the nucleation density.The following Hoffman–Lauritzen expression is normally adopted for the growth rateG ½T ðt Þ Z G 0exp KUR $ðT ðt ÞK T N Þ!exp K K g $ðT ðt ÞC T m Þ2T ðt Þ2$ðT m K T ðt ÞÞð10ÞEqs.(7)and (10)have the same form,however the values of the constants are different.The nucleation mechanism can be either homo-geneous or heterogeneous.In the case of heterogeneous nucleation,two equations are reported in the literature,both describing the nucleation density as a function of temperature [37,50]:N ðT ðt ÞÞZ N 0exp ½j $ðT m K T ðt ÞÞ (11)N ðT ðt ÞÞZ N 0exp K 3$T mT ðt ÞðT m K T ðt ÞÞ(12)In the case of homogeneous nucleation,the nucleation rate rather than the nucleation density is function of temperature,and a Hoffman–Lauritzen expression isadoptedd N ðT ðt ÞÞd t Z N 0exp K C 1ðT ðt ÞK T N Þ!exp KC 2$ðT ðt ÞC T m ÞT ðt Þ$ðT m K T ðt ÞÞð13ÞConcentration of nucleating particles is usually quite signiﬁcant in commercial polymers,and thus hetero-geneous nucleation becomes the dominant mechanism.When Kolmogoroff’s approach is followed,the number N a of active nuclei at the end of the crystal-lization process can be calculated as [48]N a ;final Zðt final 0d N ½T ðs Þd sð1K x ðs ÞÞd s (14)and the average dimension of crystalline structures can be attained by geometrical considerations.Pantani et al.[51]and Zuidema et al.[22]exploited this method to describe the distribution of crystallinity and the ﬁnal average radius of the spherulites in injection moldings of polypropylene;in particular,they adopted the following equationR Z ﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃﬃ3x a ;final 4p N a ;final 3s (15)A different approach is also present in the literature,somehow halfway between Nakamura’s and Kolmo-goroff’s models:the growth rate (G )and the kinetic constant (K )are described independently,and the number of active nuclei (and consequently the average dimensions of crystalline entities)can be obtained by coupling Eqs.(4)and (9)asN a ðT ÞZ 3ln 24p K ðT ÞG ðT Þ 3(16)where heterogeneous nucleation and spherical growth is assumed (Avrami’s index Z 3).Guo et al.[43]adopted this approach to describe the dimensions of spherulites in injection moldings of polypropylene.1.1.4.Modeling of the effect of crystallinity on rheology As mentioned above,crystallization has a dramatic inﬂuence on material viscosity.This phenomenon must obviously be taken into account and,indeed,the solidiﬁcation of a semi-crystalline material is essen-tially caused by crystallization rather than by tempera-ture in normal processing conditions.Despite of the importance of the subject,the relevant literature on the effect of crystallinity on viscosity isR.Pantani et al./Prog.Polym.Sci.30(2005)1185–12221192rather scarce.This might be due to the difﬁculties in measuring simultaneously rheological properties and crystallinity evolution during the same tests.Apart from some attempts to obtain simultaneous measure-ments of crystallinity and viscosity by special setups [52,53],more often viscosity and crystallinity are measured during separate tests having the same thermal history,thus greatly simplifying the experimental approach.Nevertheless,very few works can be retrieved in the literature in which(shear or complex) viscosity can be somehow linked to a crystallinity development.This is the case of Winter and co-workers [54],Vleeshouwers and Meijer[55](crystallinity evolution can be drawn from Swartjes[56]),Boutahar et al.[57],Titomanlio et al.[15],Han and Wang[36], Floudas et al.[58],Wassner and Maier[59],Pantani et al.[60],Pogodina et al.[61],Acierno and Grizzuti[62].All the authors essentially agree that melt viscosity experiences an abrupt increase when crystallinity degree reaches a certain‘critical’value,x c[15]. However,little agreement is found in the literature on the value of this critical crystallinity degree:assuming that x c is reached when the viscosity increases of one order of magnitude with respect to the molten state,it is found in the literature that,for iPP,x c ranges from a value of a few percent[15,62,60,58]up to values of20–30%[58,61]or even higher than40%[59,54,57].Some studies are also reported on the secondary effects of relevant variables such as temperature or shear rate(or frequency)on the dependence of crystallinity on viscosity.As for the effect of temperature,Titomanlio[15]found for an iPP that the increase of viscosity for the same crystallinity degree was higher at lower temperatures,whereas Winter[63] reports the opposite trend for a thermoplastic elasto-meric polypropylene.As for the effect of shear rate,a general agreement is found in the literature that the increase of viscosity for the same crystallinity degree is lower at higher deformation rates[62,61,57].Essentially,the equations adopted to describe the effect of crystallinity on viscosity of polymers can be grouped into two main categories:–equations based on suspensions theories(for a review,see[64]or[65]);–empirical equations.Some of the equations adopted in the literature with regard to polymer processing are summarized in Table1.Apart from Eq.(17)adopted by Katayama and Yoon [66],all equations predict a sharp increase of viscosity on increasing crystallinity,sometimes reaching inﬁnite (Eqs.(18)and(21)).All authors consider that the relevant variable is the volume occupied by crystalline entities(i.e.x),even if the dimensions of the crystals should reasonably have an effect.1.1.5.Modeling of the molecular orientationOne of the most challenging problems to present day polymer science regards the reliable prediction of molecular orientation during transformation processes. Indeed,although pressure and velocity distribution during injection molding can be satisfactorily described by viscous models,details of the viscoelastic nature of the polymer need to be accounted for in the descriptionTable1List of the most used equations to describe the effect of crystallinity on viscosityEquation Author Derivation Parameters h=h0Z1C a0x(17)Katayama[66]Suspensions a Z99h=h0Z1=ðx K x cÞa0(18)Ziabicki[67]Empirical x c Z0.1h=h0Z1C a1expðK a2=x a3Þ(19)Titomanlio[15],also adopted byGuo[68]and Hieber[25]Empiricalh=h0Z expða1x a2Þ(20)Shimizu[69],also adopted byZuidema[22]and Hieber[25]Empiricalh=h0Z1Cðx=a1Þa2=ð1Kðx=a1Þa2Þ(21)Tanner[70]Empirical,basedon suspensionsa1Z0.44for compact crystallitesa1Z0.68for spherical crystallitesh=h0Z expða1x C a2x2Þ(22)Han[36]Empiricalh=h0Z1C a1x C a2x2(23)Tanner[71]Empirical a1Z0.54,a2Z4,x!0.4h=h0Zð1K x=a0ÞK2(24)Metzner[65],also adopted byTanner[70]Suspensions a Z0.68for smooth spheresR.Pantani et al./Prog.Polym.Sci.30(2005)1185–12221193。

关于实验是检验真理的唯一标准英语作文

关于实验是检验真理的唯一标准英语作文全文共3篇示例，供读者参考篇1Experiment: The Only Yardstick for Measuring TruthTruth, that elusive and coveted prize that humanity has chased after for millennia. We've constructed elaborate philosophies, devised ingenious thought experiments, and spent countless hours pondering and debating what constitutes truth and how to discern it from fiction. Yet, amid this intellectual odyssey, one approach has emerged as the undisputed champion, a beacon of light cutting through the fog of speculation and conjecture – the scientific experiment.As a student, I've been taught to revere the sanctity of the scientific method, to view it as the ultimate arbiter of truth in a world often clouded by biases, assumptions, and unfounded beliefs. Through rigorous experimentation, we can strip away the veneers of preconceived notions and subject our hypotheses to the unforgiving crucible of empirical evidence.The strength of the experiment lies in its objectivity and replicability. It transcends the limitations of individualperspectives, cultural biases, and ideological leanings, offering a universal language that any rational mind can comprehend. When conducted with precision and adherence to established protocols, an experiment becomes a testament to the pursuit of truth, a beacon guiding us through the labyrinth of uncertainty.Consider the countless breakthroughs and paradigm shifts that have reshaped our understanding of the world, from Galileo's revolutionary observations of the heavens to the groundbreaking experiments of Marie Curie that unveiled the mysteries of radioactivity. Each of these monumental discoveries was forged not in the realm of abstract theorizing but through meticulous experimentation, where hypotheses were put to the ultimate test, and nature itself was allowed to speak its truth.The beauty of the experiment lies in its ability to challenge our preconceptions and shatter long-held beliefs. It acts as a bulwark against the insidious influence of dogma, forcing us to confront reality head-on and embrace the uncomfortable truths that may contradict our cherished notions. The annals of science are replete with examples of experiments that have upended conventional wisdom, from the earth's revolution around the sun to the counterintuitive principles of quantum mechanics.Moreover, the experiment fosters a culture of intellectual humility, a recognition that our understanding of the universe is ever-evolving and subject to constant refinement. It reminds us that truth is not a static entity to be grasped once and for all but a dynamic pursuit, a journey of continuous exploration and discovery. Through experimentation, we acknowledge the limitations of our current knowledge and remain open to the possibility of revising our beliefs in the face of new evidence.Yet, the power of the experiment extends far beyond the realms of natural sciences. In the social sciences, carefully designed experiments have illuminated the intricate workings of human behavior, shedding light on topics as diverse as decision-making, social dynamics, and cognitive biases. By isolating and manipulating variables in controlled environments, researchers can tease apart the complex tapestry of human interactions, uncovering truths that would otherwise remain obscured by the noise of everyday life.Even in the abstract domains of mathematics and logic, the experiment plays a crucial role. Through the construction of formal systems and the derivation of theorems, mathematicians and logicians engage in a form of intellectual experimentation, subjecting their axioms and conjectures to the rigors of logicalscrutiny. The truth of a mathematical statement is not determined by mere assertion but by its ability to withstand the relentless probing of logical deduction and proof.Of course, the experiment is not without its limitations. It is a tool, and like any tool, it can be misused or misinterpreted. Flawed experimental designs, measurement errors, and selective reporting of results can lead us astray, obscuring the truth rather than revealing it. This is why the scientific community places such emphasis on rigorous peer review, replication studies, and a commitment to transparency and integrity in the experimental process.Furthermore, there are realms of inquiry where the experiment may not be applicable or practical, such as in the study of historical events or in the exploration of certain metaphysical and philosophical questions. In these domains, we must rely on other modes of inquiry, such as textual analysis, logical argumentation, and reasoned discourse, while maintaining a healthy skepticism and a willingness to revise our beliefs in the face of new evidence.Yet, despite these caveats, the experiment remains the gold standard for testing truth, a beacon that guides us through the murky waters of uncertainty and conjecture. It is a testament tothe human spirit's insatiable curiosity and our relentless pursuit of knowledge, a pursuit that has yielded countless wonders and revelations about the universe we inhabit.As a student, I have been indelibly shaped by this reverence for the experiment and the scientific method. It has instilled in me a deep appreciation for the power of evidence, a respect for the rigor of the scientific process, and a commitment to intellectual honesty. It has taught me to question assumptions, to embrace uncertainty, and to remain open to revising my beliefs in the face of compelling evidence.More importantly, the experiment has imbued me with a sense of wonder and awe at the grandeur of the universe and the boundless potential of human inquiry. Each time a hypothesis is tested, a new door is opened, revealing glimpses of truth that were previously obscured. It is a journey of endless discovery, where each answer begets a multitude of new questions, propelling us ever forward in our quest for understanding.In a world often beset by dogmatism, misinformation, and the allure of convenient fictions, the experiment stands as a beacon of hope, a reminder that truth is not a matter of opinion or belief but a pursuit rooted in evidence and reason. It is a call to embrace intellectual humility, to shed our preconceptions,and to fearlessly confront the unknown, armed with the tools of scientific inquiry and a steadfast commitment to uncovering the truths that lie beyond the veil of our limited perceptions.So, as I embark on my academic and professional journey, I carry with me this unwavering conviction: the experiment is not merely a tool for testing truth but a way of life, a embodiment of the human spirit's insatiable thirst for knowledge and understanding. It is a torch that illuminates the path forward, guiding us towards a future where truth reigns supreme, and the boundaries of our understanding are continually pushed ever outward, into the vast expanse of the unknown.篇2Experimentation: The Sole Criterion of Truth?As a student grappling with the complexities of epistemology – the study of knowledge and its acquisition – I find myself drawn to the notion that experimentation is the sole criterion of truth. This assertion challenges the traditional methods of acquiring knowledge and raises pertinent questions about the nature of truth itself. In this essay, I will delve into the merits and limitations of this stance, drawing upon philosophicalinsights and empirical evidence to present a comprehensive analysis.The proposition that experimentation is the sole arbiter of truth finds its roots in the empirical tradition, which emerged during the Scientific Revolution of the 16th and 17th centuries. Thinkers such as Francis Bacon and René Descartes advocated for a systematic and methodical approach to understanding the natural world, rejecting the authority of ancient texts and embracing the power of observation and experimentation.Proponents of this view assert that truth can only be established through controlled, replicable experiments that test hypotheses against empirical data. This approach places a premium on objectivity, rigorous methodology, and the ability to reproduce results. By subjecting our assumptions to the scrutiny of empirical inquiry, we can weed out unfounded beliefs and superstitions, allowing us to uncover the underlying principles that govern the universe.The success of the scientific method in unveiling the mysteries of the natural world lends credence to this perspective. Through experimentation, we have unraveled the intricacies of physics, chemistry, biology, and myriad other disciplines, enabling technological advancements that have transformed ourlives. The theories and laws derived from empirical investigations have withstood the test of time, serving as the bedrock of our understanding of the universe.Moreover, the reliance on experimentation fosters a spirit of skepticism and critical thinking, which are essential for the pursuit of truth. By constantly challenging our assumptions and subjecting them to empirical verification, we safeguard against the pitfalls of dogmatism and blind acceptance of authority. This approach encourages intellectual humility, as even the most well-established theories must be continuously scrutinized and refined in the face of new evidence.However, it would be remiss to adopt an unwavering stance on experimentation as the sole criterion of truth without acknowledging its limitations and the existence of other legitimate modes of inquiry. While experimentation excels in the realm of the natural sciences, it may fall short in addressing questions of ethics, aesthetics, and metaphysics, which often defy empirical verification.For instance, how can we experimentally determine the inherent value of human life or the moral implications of our actions? The realm of ethics and morality is rooted in philosophical reasoning, cultural traditions, and subjectiveexperiences, which may not lend themselves readily to experimental methodologies. Similarly, our appreciation of art and beauty, while grounded in neural and psychological processes, transcends mere empirical analysis and involves subjective interpretations shaped by individual experiences and cultural contexts.Furthermore, the pursuit of truth is not solely confined to the observable and measurable aspects of reality. Metaphysical inquiries into the nature of existence, consciousness, and the fundamental constituents of the universe often engage with realms that lie beyond the reach of direct experimentation. While empirical evidence can inform and constrain our metaphysical theories, the ultimate truths about the origin and essence of reality may elude the confines of the experimental method.It is also important to acknowledge the inherent limitations of experimentation itself. Despite our best efforts to maintain objectivity and rigor, our experiments are subject to the constraints of our current technological capabilities, theoretical frameworks, and human biases. The history of science is replete with instances where flawed experimental designs, faulty data analysis, or cognitive biases led to erroneous conclusions that were later overturned by more rigorous investigations.Moreover, the reductionist approach inherent in experimentation may fail to capture the holistic and emergent properties of complex systems, leading to an incomplete understanding of the phenomena under study. The interplay of multiple factors, non-linear dynamics, and the inherent unpredictability of certain systems may defy the controlled conditions and simplifying assumptions of experiments, necessitating the integration of alternative modes of inquiry.In light of these considerations, a more nuanced perspective emerges: while experimentation is an indispensable tool in our quest for truth, it should not be regarded as the sole criterion. Instead, we must embrace a pluralistic approach that recognizes the complementary roles of various modes of inquiry, each contributing to our understanding of the world in unique and invaluable ways.Philosophical reasoning, introspection, and subjective experiences offer insights into the realms of ethics, aesthetics, and consciousness, domains that may elude the grasp of empirical investigation. Cultural traditions and indigenous ways of knowing can provide alternative perspectives and enrich our understanding of the human experience. Mathematical and logical reasoning can unveil truths about abstract concepts andformal systems, transcending the boundaries of the physical world.Ultimately, the pursuit of truth is a multifaceted endeavor that requires a synthesis of diverse modes of inquiry, each illuminating different facets of reality. Experimentation remains a pivotal component of this pursuit, providing a rigorous and systematic method for testing hypotheses and uncovering the underlying principles that govern the natural world. However, it is not the sole criterion of truth, but rather a powerful tool that must be wielded in conjunction with other modes of inquiry to achieve a more comprehensive and holistic understanding of the world we inhabit.As students and seekers of knowledge, our task is to cultivate a spirit of intellectual humility, recognizing the limitations of any single approach while embracing the richness and diversity of human inquiry. By integrating the insights gleaned from experimentation with those derived from philosophical, cultural, and subjective modes of understanding, we can navigate the complexities of truth with greater wisdom and depth, ultimately enriching our collective knowledge and enhancing our ability to comprehend the mysteries that surround us.篇3Experiment as the Sole Criterion of TruthThe quest for truth and knowledge has been an enduring pursuit throughout human history. As we navigate the complexities of the natural world, we are confronted with numerous assertions, theories, and beliefs that compete for our acceptance. In this landscape, the question arises: How can we discern truth from falsehood? Is there a universal standard by which we can evaluate the validity of claims? Many philosophers and scientists have grappled with this fundamental inquiry, and one perspective that has gained significant traction is the notion that experiment is the sole criterion of truth.At first glance, this proposition may seem overly simplistic or even radical. After all, the realm of human knowledge encompasses a vast array of disciplines, from the abstract realms of mathematics and philosophy to the tangible domains of the natural sciences. How can a single standard encompass such diversity? However, upon closer examination, the argument for experiment as the ultimate arbiter of truth holds considerable weight.The essence of this perspective lies in the recognition that empirical evidence, derived from carefully controlled and replicable experiments, provides the most reliable foundation for establishing objective truth. Unlike mere speculation, anecdotal accounts, or subjective interpretations, experiments offer a systematic and rigorous approach to testing hypotheses and uncovering the fundamental principles that govern the universe.One of the strongest arguments in favor of this view is the remarkable success of the scientific method, which relies heavily on experimentation. Throughout history, countless discoveries and technological advancements have been made possible through the application of experimental techniques. From the groundbreaking work of pioneers like Galileo and Newton to the cutting-edge research in fields like particle physics and molecular biology, experiments have consistently yielded insights that have reshaped our understanding of the world.Moreover, the power of experimentation lies in its ability to challenge and refine existing theories. By subjecting hypotheses to rigorous testing and scrutiny, experiments can either confirm or refute proposed explanations. This process of continuous questioning and verification is essential for advancing ourknowledge and ensuring that our beliefs align with empirical reality.Critics of this perspective may argue that not all domains of knowledge are amenable to experimental investigation. For instance, how can one conduct experiments to explore abstract philosophical concepts or subjective experiences? While this objection holds some merit, it is important to recognize that even in these realms, the principles of empiricism and verifiability remain paramount. Philosophical arguments and theories that cannot be subjected to any form of empirical scrutiny or logical analysis run the risk of becoming mere speculation or dogma.Furthermore, the notion of experiment as the sole criterion of truth does not necessarily preclude other forms of inquiry or knowledge acquisition. Rather, it suggests that any claim, whether derived from reason, intuition, or revelation, must ultimately be subjected to the litmus test of empirical verification through experimentation. This process may involve indirect methods, such as the analysis of observable phenomena or the construction of logical arguments based on empirical premises.Another compelling argument in favor of this perspective is the inherent objectivity and universality of experimental results. Unlike subjective interpretations or culturally specific beliefs,well-designed experiments transcend personal biases and can be replicated and verified by researchers across different geographical and cultural contexts. This universality of empirical evidence fosters a shared understanding of the natural world and promotes scientific collaboration on a global scale.However, it is crucial to acknowledge the limitations and potential pitfalls associated with experimental research. Experiments can be influenced by a variety of factors, including flawed experimental designs, measurement errors, and unconscious biases. Additionally, the interpretation of experimental results may be subject to varying theoretical frameworks or philosophical assumptions. These challenges underscore the importance of rigorous peer review, replication studies, and a commitment to continually refining experimental methodologies.Despite these limitations, the weight of evidence supporting the primacy of experimentation as the ultimate arbiter of truth is overwhelming. From the remarkable achievements of modern science to the consistent ability of experiments to challenge and revise longstanding beliefs, the empirical approach has proven itself as the most reliable path to uncovering objective truth.In conclusion, the proposition that experiment is the sole criterion of truth represents a powerful and compelling perspective. While acknowledging the limitations and potential objections, the overwhelming success of the scientific method and the inherent objectivity of empirical evidence strongly support this view. As we continue to explore the mysteries of the universe and seek to expand the boundaries of human knowledge, the principles of experimentation and empirical verification must remain at the forefront of our endeavors. Only through a steadfast commitment to empiricism and a willingness to subject our beliefs to rigorous testing can we hope to uncover the deepest truths of the natural world.。

希腊古瓮颂翻译及简要赏析希腊古瓮颂修辞赏析

希腊古瓮颂翻译及简要赏析希腊古瓮颂修辞赏析希腊古瓮颂你委身“寂静”的、完美的处子，受过了“沉默”和“悠久”的抚育，呵，田园的史家，你竟能铺叙一个如花的故事，比诗还瑰丽：在你的形体上，岂非缭绕着古老的传说，以绿叶为其边缘，讲着人，或神，敦陂或阿卡狄？呵，是怎样的人，或神！在乐舞前多热烈的追求！少女怎样地逃躲！怎样的风笛和鼓铙！怎样的狂喜！听见的乐声虽好，但若听不见却更和美，所以，吹吧，柔情的风笛；不是奏给耳朵听，而是更甜，它给灵魂奏出无声的乐曲；树下的美少年呵，你无法中断你的歌，那树木也落不了叶子；卤莽的恋人，你永远，永远吻不上，虽然够接近了——但不必心酸；她不会老，虽然你不能如愿以偿，你将永远爱下去，她也永远秀丽！呵，幸福的树木！你的枝叶不会剥落，从不曾离开春天，幸福的吹笛人也绝不停歇，他的歌曲永远是那么新鲜；呵，更为幸福的、幸福的爱！永远热烈，正等待情人宴飨，永远热情的心跳，永远年轻；幸福的是这一切超凡的情态：它不会而使心灵餍足和悲伤，没有炽热的头脑，焦渴的嘴唇。

这些人是谁呵，都去赴祭祀？这作牺牲的小牛，对天鸣叫，你要牵它到哪儿，神秘的祭司？花环缀满着它光滑的身腰。

主要是从哪个傍河傍海的小镇，或哪个静静的堡寨的山村，来了这些人，在这敬神的清早？呵，小镇，你的街道永远恬静；再也不可能将回来一个灵魂告诉人你何以是怎么寂寥。

哦，希腊的形状！唯美的观照上面缀有石雕的男人和女人，还有林木，和践踏过的青草；沉默的形体呵，你象是“永恒”使人超越思想：呵，冰冷的牧歌！等暮年使这一世代都凋落，只有你如旧；在另外的一些深沉中，你会抚慰后人说：“美即是真，真即是美，”这就包括你们所知道、和该知道的一切。

(查良铮译，选自《济慈诗选》，人民文学出版社，1958年)一个古瓮会给我们带来什么呢？造型的浪漫和雕饰的华美？一般来说只有这些。

但是，在英国大点诗人济慈（1795年---1821年）眼里可就不一样了，竟然铺叙出一篇华美的乐章——《希腊古瓮颂》。

光于金属的英语作文

光于金属的英语作文Radiance of MetalsMetals have long captivated the human imagination, their gleaming surfaces and diverse properties inspiring awe and fascination. From the ancient forges of blacksmiths to the high-tech laboratories of modern materials science, the allure of metals has endured, shaping the course of human civilization. In this essay, we shall explore the radiance of metals, delving into their unique characteristics, their historical significance, and their enduring impact on our world.At the heart of metals' allure lies their remarkable properties. Their high thermal and electrical conductivity make them indispensable in a wide range of applications, from power transmission to electronic devices. The malleability and ductility of certain metals allow them to be shaped and molded into intricate forms, enabling the creation of breathtaking works of art and engineering. The strength and durability of metals have made them essential building blocks for structures, vehicles, and tools, underpinning the very foundations of our modern society.Beyond their practical applications, metals have also held a deepsymbolic significance throughout history. Gold, with its lustrous glow, has long been associated with wealth, power, and the divine. The gleaming silver of coins and jewelry has been a symbol of elegance and refinement, while the steely gray of iron has come to represent the industrial might of nations. The very names of some metals, such as titanium and chromium, evoke a sense of strength and resilience.The history of human civilization is inextricably linked to the development and mastery of metals. The Bronze Age, marked by the advent of bronze tools and weapons, ushered in a new era of technological advancement and social complexity. The Iron Age that followed saw the rise of empires and the forging of mighty swords and armor. In more recent times, the Industrial Revolution was fueled by the large-scale production and application of metals, from the steel that built skyscrapers to the aluminum that revolutionized transportation.The radiance of metals extends beyond their physical properties and historical significance. In the realm of art and design, metals have been employed to create some of the most breathtaking and iconic works of human expression. The shimmering gold of Byzantine mosaics, the intricate metalwork of medieval cathedrals, and the sleek, modern designs of contemporary architecture all bear witness to the enduring allure of metals.Moreover, the study of metals has been a driving force behind scientific and technological advancements. Materials science, a field that delves into the fundamental properties and behavior of materials, has revolutionized our understanding of metals, leading to the development of new alloys, the refinement of manufacturing processes, and the exploration of cutting-edge applications.In the realm of sustainable development, metals have also played a crucial role. Many metals are highly recyclable, allowing for the conservation of natural resources and the reduction of waste. The development of lightweight, high-strength metals has enabled the creation of more fuel-efficient vehicles and structures, contributing to the ongoing efforts to mitigate the impact of human activities on the environment.As we look to the future, the radiance of metals continues to captivate and inspire. From the development of advanced materials for space exploration to the creation of innovative medical devices, the versatility and potential of metals remain boundless. The ongoing quest to harness the power of metals, to push the boundaries of their capabilities, and to unlock new realms of possibility is a testament to the enduring fascination that these remarkable materials hold for us.In conclusion, the radiance of metals is a multifaceted phenomenon,encompassing their physical properties, historical significance, artistic expression, and scientific advancement. As we continue to explore and exploit the wonders of these materials, we can marvel at the ways in which they have shaped our world and continue to hold the promise of a brighter, more innovative future.。

化学动力学原理（第二版）说明书

Principles of Chemical KineticsPrinciplesofChemicalKinetics Second EditionJames E.HouseIllinoisStateUniversityandIllinois WesleyanUniversityAMSTERDAM • BOSTON • HEIDELBERG • LONDONNEW YORK • OXFORD • PARIS • SAN DIEGOSAN FRANCISCO • SINGAPORE • SYDNEY • TOKYOAcademic Press is an imprint of ElsevierAcademic Press is an imprint of Elsevier30Corporate Drive,Suite400,Burlington,MA01803,USA525B Street,Suite1900,San Diego,CA92101-4495,USA84Theobald’s Road,London WC1X8RR,UKThis book is printed on acid-freeCopyrightß2007,Elsevier Inc.All rights reserved.No part of this publication may be reproduced or transmitted in any form or by any means,electronic or mechanical,including photocopy,recording,or any information storage and retrieval system,without permission in writing from the publisher. Permissions may be sought directly from Elsevier’s Science&Technology Rights Department in Oxford,UK:phone:(þ44)1865843830,fax:(þ44)1865853333,E-mail:************************.You may also complete your request on-linevia the Elsevier homepage(http:==),by selecting‘‘Support&Contact’’then‘‘Copyright and Permission’’and then‘‘Obtaining Permissions.’’Library of Congress Cataloging-in-Publication DataHouse,J.E.Principles of chemical kinetics/James E.House.–2nd ed.p.cm.Includes index.ISBN:978-0-12-356787-1(hard cover:alk.paper) 1.Chemical kinetics.I.Title. QD502.H6820075410.394–dc222007024528 British Library Cataloguing-in-Publication DataA catalogue record for this book is available from the British Library.ISBN:978-0-12-356787-1For information on all Academic Press publicationsvisit our web site at Printed in the United States of America07080910987654321Preface Chemical kinetics is an enormous W eld that has been the subject of many books,including a series that consists of numerous large volumes.To try to cover even a small part of the W eld in a single volume of portable size is a di Y cult task.As is the case with every writer,I have been forced to make decisions on what to include,and like other books,this volume re X ects the interests and teaching experience of the author.As with the W rst edition,the objective has been to provide an introduc-tion to most of the major areas of chemical kinetics.The extent to which this has been done successfully will depend on the viewpoint of the reader. Those who study only gas phase reactions will argue that not enough material has been presented on that topic.A biochemist who specializes in enzyme-catalyzed reactions may W nd that research in that area requires additional material on the topic.A chemist who specializes in assessing the in X uence of substituent groups or solvent on rates and mechanisms of organic reactions may need other tools in addition to those presented. In fact,it is fair to say that this book is not written for a specialist in any area of chemical kinetics.Rather,it is intended to provide readers an introduction to the major areas of kinetics and to provide a basis for further study.In keeping with the intended audience and purposes,derivations are shown in considerable detail to make the results readily available to students with limited background in mathematics.In addition to the signi W cant editing of the entire manuscript,new sections have been included in several chapters.Also,Chapter9‘‘Additional Applications of Kinetics,’’has been added to deal with some topics that do not W t conveniently in other chapters.Consequently,this edition contains substantially more material,including problems and references,than the W rst edition.Unlike the W rst edition,a solution manual is also available.As in the case of the W rst edition,the present volume allows for variations in the order of taking up the material.After the W rst three chapters,thevvi Prefaceremaining chapters can be studied in any order.In numerous places in the text,attention is drawn to the fact that similar kinetic equations result for di V erent types of processes.As a result,it is hoped that the reader will see that the assumptions made regarding interaction of an enzyme with a substrate are not that di V erent from those regarding the adsorption of a gas on the surface of a solid when rate laws are derived.The topics dealing with solid state processes and nonisothermal kinetics are covered in more detail than in some other texts in keeping with the growing importance of these topics in many areas of chemistry.These areas are especially important in industrial laboratories working on processes involving the drying, crystallizing,or characterizing of solid products.It is hoped that the present volume will provide a succinct and clear introduction to chemical kinetics that meets the needs of students at a variety of levels in several disciplines.It is also hoped that the principles set forth will prove useful to researchers in many areas of chemistry and provide insight into how to interpret and correlate their kinetic data.Contents1Fundamental Concepts of Kinetics11.1Rates of Reactions21.2Dependence of Rates on Concentration41.2.1First-Order51.2.2Second-Order81.2.3Zero-Order101.2.4N th-Order Reactions131.3Cautions on Treating Kinetic Data131.4E V ect of Temperature161.5Some Common Reaction Mechanisms201.5.1Direct Combination211.5.2Chain Mechanisms221.5.3Substitution Reactions231.6Catalysis27References for Further Reading30 Problems31 2Kinetics of More Complex Systems372.1Second-Order Reaction,First-Order in Two Components372.2Third-Order Reactions432.3Parallel Reactions452.4Series First-Order Reactions472.5Series Reactions with Two Intermediates532.6Reversible Reactions582.7Autocatalysis642.8E V ect of Temperature69References for Further Reading75 Problems75viiviii Contents3Techniques and Methods793.1Calculating Rate Constants793.2The Method of Half-Lives813.3Initial Rates833.4Using Large Excess of a Reactant(Flooding)863.5The Logarithmic Method873.6E V ects of Pressure893.7Flow Techniques943.8Relaxation Techniques953.9Tracer Methods983.10Kinetic Isotope E V ects102References for Further Reading107 Problems108 4Reactions in the Gas Phase1114.1Collision Theory1114.2The Potential Energy Surface1164.3Transition State Theory1194.4Unimolecular Decomposition of Gases1244.5Free Radical or Chain Mechanisms1314.6Adsorption of Gases on Solids1364.6.1Langmuir Adsorption Isotherm1384.6.2B–E–T Isotherm1424.6.3Poisons and Inhibitors1434.7Catalysis145References for Further Reading147 Problems148 5Reactions in Solutions1535.1The Nature of Liquids1535.1.1Intermolecular Forces1545.1.2The Solubility Parameter1595.1.3Solvation of Ions and Molecules1635.1.4The Hard-Soft Interaction Principle(HSIP)1655.2E V ects of Solvent Polarity on Rates1675.3Ideal Solutions1695.4Cohesion Energies of Ideal Solutions1725.5E V ects of Solvent Cohesion Energy on Rates1755.6Solvation and Its E V ects on Rates1775.7E V ects of Ionic Strength182Contents ix5.8Linear Free Energy Relationships1855.9The Compensation E V ect1895.10Some Correlations of Rates with Solubility Parameter191References for Further Reading198 Problems199 6Enzyme Catalysis2056.1Enzyme Action2056.2Kinetics of Reactions Catalyzed by Enzymes2086.2.1Michaelis–Menten Analysis2086.2.2Lineweaver–Burk and Eadie Analyses2136.3Inhibition of Enzyme Action2156.3.1Competitive Inhibition2166.3.2Noncompetitive Inhibition2186.3.3Uncompetitive Inhibition2196.4The E V ect of pH2206.5Enzyme Activation by Metal Ions2236.6Regulatory Enzymes224References for Further Reading226 Problems227 7Kinetics of Reactions in the Solid State2297.1Some General Considerations2297.2Factors A V ecting Reactions in Solids2347.3Rate Laws for Reactions in Solids2357.3.1The Parabolic Rate Law2367.3.2The First-Order Rate Law2377.3.3The Contracting Sphere Rate Law2387.3.4The Contracting Area Rate Law2407.4The Prout–Tompkins Equation2437.5Rate Laws Based on Nucleation2467.6Applying Rate Laws2497.7Results of Some Kinetic Studies2527.7.1The Deaquation-Anation of[Co(NH3)5H2O]Cl32527.7.2The Deaquation-Anation of[Cr(NH3)5H2O]Br32557.7.3The Dehydration of Trans-[Co(NH3)4Cl2]IO3 2H2O2567.7.4Two Reacting Solids259References for Further Reading261 Problems262x Contents8Nonisothermal Methods in Kinetics2678.1TGA and DSC Methods2688.2Kinetic Analysis by the Coats and Redfern Method2718.3The Reich and Stivala Method2758.4A Method Based on Three(a,T)Data Pairs2768.5A Method Based on Four(a,T)Data Pairs2798.6A Di V erential Method2808.7A Comprehensive Nonisothermal Kinetic Method2808.8The General Rate Law and a Comprehensive Method281References for Further Reading287 Problems288 9Additional Applications of Kinetics2899.1Radioactive Decay2899.1.1Independent Isotopes2909.1.2Parent-Daughter Cases2919.2Mechanistic Implications of Orbital Symmetry2979.3A Further Look at Solvent Properties and Rates303References for Further Reading313 Problems314 Index317。